Cofferdam and method of construction



March 25, 1930. w. 5,' MONROE ET AL Filed O01.. 27, 1927 COFFER DAM AND METHOD OF CONSTRUCTION 3 Sheets-Sheet 1 iwi vCH:

March 25, 1930. w. s. MONROE ET AL COFFEE DAM AND METHOD OF CONSTRUCTION Filed oct. v, 1927 3 Sheets-Sheet 2 xnaN .H Y

March 25, 1930. w. s.l MONROE ET AL l COFFER DAM AND DIIETHOD OF CONSTRUCTION Filed Oct. 27, 1927 3 Sheets-Sheet 3 Illu Patented Mar. 25, 1930 IWTD STATES PATENT orifice WILLIAM Si, MONROE, OF CHICAGO, AND JOI-IN C. SANDERSON, OF EVANSTON, ILLINOIS,

ASSIGNORS TO SARGENT 8c LUNDY, INCORPORATED, OF CHICAGO, ILLINOIS, A; CO3-,A 1

PORATION OF ILLINOIS COFFERDAM AND METHOD OF CONSTRUCTION Application inea october 27, 1927.' serial No. 229,059.

This invention relates to Colfer dams, and more particularlyto the means and method of constructing a coffer dam and erecting a permanent structure as removal of the excavated material progresses.

As is well understood in this art, coffer dams are used under conditions where the enclosing sheet pile structure lis subjected to severe pressures from the outside. It is essential, therefore, that the sheet pile structure be effectively braced so as to prevent collapse of thedam and insure safety of the workmen. To obtain this result it is the resent practice to install heavy horizontal racing as the excavation progresses', which necessity we avoid by our invention.

The purpose of a coffer-dam is to main- Y tain an open working space in which to `build structures that extend some distance below the surface of the water or the ground. lVhen the sheet piling of a coifer-dam is first driven it is not subjected to any appreciable external pressures since such pressures are counteracted by the pressure of the material enclosed by the coffendam.V As the material is removed from within the dam, however, `it is subjected to external pressure. This external pressure increases progressively with the removal of the excavated material.

The present practice in construction of coffer-dams is to drive the sheet piling three or four feet outside of the line of the finished surface of the concrete. This is to allow for the installation of wales or other bracing members to take the earth pressure againstthe sheeting and also to allow room for the construction of forms for the concrete. This means that the colfer-dam has to be very much larger than the size of the finished concrete and the volume of excavated material is therefore greater than that of the finished concrete. It also means that a considerable amount of back filling has to be done after the concrete is finished. The horizontal braces and struts in the ordinary coifer dam construction have to be placed so close together, especially in the flower part of the excavation, that they seriously interfere with the work of excavating.

W e have found that it is possible by driving steel beams'or steel piles to bracethe sheet piling and by arranging these so that they can be built into thepermanent structure and properly bracing these steel piles, the

number of horizontal struts used in the coiferdam can be very greatly reduced and the sheet piling can be driven immediately outside of the fini shed line of concrete, Y

This method greatly reduces the amount of material to be excavated and also facili tates and expedites the process ofexcavating because the interference caused by they horizontal struts is very much less than in the ordinary types of coifer-dam. f

With our method'of construction the sheet piling can be used as the outside form for the concrete which greatly reduces the amount of form work, and-by painting the sheet piling, or covering it with paper, it 'can be pulled out after the worlr is inishedand used over again. @ur method therefore effects a very material saving over the present practice lin both time and material inthe excavation, form work, and inthe construction of the coifer-dam with a corresponding saving in the cost of the compietedstructure. f By our methodthe forms for the concrete Walls can be erected within the Cotter-damas the exca vation progresses. and if desired the concrete canbe poured as excavation of the material progresses, which further facilitates and exA pedites the work. Further objects and advantages will appear from'the detail-description4 f In the drawingsz-w F ig. l is a horizontal sectional view taken through a cofler-dain constructed in accord-v ance with our invention .on a plane adjacent the top of the dam; A Fig. 2 is a fragmentary vertical sectional view through the coifeldam,` Fig. 3 is a view similar to Fig. 2 through a modified form of dam;

Fig. i is a detail of one ofthe sheet piles used in' constructing the dam;

Fig. 5 is an end view of one of the brace members;

yFig. 6 is a fragmentary outer face View of the lower portion of one of the brace meme"V bers;

Fig. 7 is a fragmentary sectional view of another modiliedform of coEer-dam;

Fig. 8 is a fragmentary sectional view of a third modified form of coHer-dam; and

Fig. 9 is a plan View of a fourth modified form of Colfer-dam, partly broken away and in section.

In constructing the coffer-dam we first provide an outer structure 1 formed of metal or wood sheet piles which are driven into the ground to the proper depth and on the lines of the permanent structure to be erected, this pile structure enclosing the material to be removed. The piles 2 used in this structure maybe of any suitable or preferred type. In Figure 4 we have illustrated a type of pile which we have found to be very satisfactory. This pile is rolled from steel and includes a fiat body 3 having lateral angularly disposed flanges 4 and 5. One of the flanges, as flange 5, is provided, at its outer edge, with an enlargement forming a substantially circular socket 6 for reception of a correspondingly shaped bead 7 at the outer edge of ange 4,

it being understood that bead 7 engages into socket 6 of an adjacent pile. In this manner the piles are locked together as they are driven and form a substantially water tight enclosure.

After the pile structure 1 has been com-y pleted a plurality of brace members 8 are driven within the pile structure parallel to and spaced a short distance from the walls thereof. These brace members 8 may be of any suitable form but are preferably in the form of I -beams which we have found to be very satisfactory for this purpose as possessing `great strength and being readily driven into the soil. Preferably, though not necessarily, each of the members 8 is provided, adjacent its lower end, with a plate'9 which is secured on the outer face of the brace member by riveting or in any other suitable or preferred manner. This plate may vary considerably in size and shape though we find that a plate of substantially rectangular shape is very satisfactory. The plate 9 is shown as disposed across the outer faceof brace member 8 at right angles thereto, -but this plate may be disposed on either the inner face or the outer face of member 8. The plate 9 applied in this manner readily enters' the soil when the brace member is driven and acts to increase the bearing capacity of the lower end of brace 8 and as an anchor to firmly secure the lower end portion of the brace member in the ground and hold it against either inward or outward movement. Preferably the brace members 8 are of such length as to extend a short distance above the sheet piles 2.

. After the sheet pile structure has been erected and the brace members have been driven, in the manner described, the material enclosed by the sheet pile structure is excavated or removed.

In accordance with our invention, after the enclosed material has been removed to a slight depth, spacing members or blocks 10 of hard wood or other suitable material are inserted between the brace members 8 and the fiat inner faces of the body portion 3 of certain of the sheet piles 2. Wales 11, :which may be formed of I-beams, are'then placed along the sides of the enclosure and'bear upon the inner faces of the brace members 8. rIhe wales at opposite sides of the enclosure are heldl apart by cross beams 12 provided at their ends with upper and lower plates 18 secured thereto and projecting beyond the beams. The plates extend across the upper and lower edges of metal plates 14 and 15 bearing against the end of the beam 12 and the inner faces or heads of the wales 11, re-l spectively. Steel wedges 16 are driven between the plates 14 and 15 and exert great pressure thereon so as to effectively brace the wales 11, and consequently the upper por Vtions of the brace members 8, against inward movement. As removal of the material progresses additional blocks 10 are inserted between the brace members 8 and the sheet piles 2 of the structure 1. In view of the fact that the upper portions of the brace members are effectively held against inward Y movement, and thelower portions ofthese members are driven into the ground `well below the bottom of the excavation, the in* termediateV blocks 10V are effectivelyv held against inward movement and serve to very effectively brace the intermediate portion of the sheet lpile structure. In this manner the completionv of the reinforcement for the sheet pile structure continues simultaneously with the removal of the material, and the bracing of the structure progresses in accordance with the progress of removal of the material and increase of pressure on the sheet pile structure. rlhis renders it possible to remove the material and to simultaneously reinforce the sheet pile structure in accordance with' increase in external pressure thereon, effecting a very material'saving in time and labor over the present method. VIt is also to be noted that the interior of the cofer-dam is unobstructed for practically its entire depth, which greatly facilitates removal of the material, particularly when excavating soil and analogous materials.

After the removal of the material has been completed, a base 17 of concrete, or other suitable material, is constructed at the bot-A structure as a `whole to external pressures. rlhe side walls 18 may bepoured `after the removal of the material has been completed, suitable forms being Yset up inside of the brace members 8 as will be readily understood, or these walls may be pouredl progressively as the removal of the material proceeds. In theV latter case, after the material has been removed to a depth corresponding approximately to the distance between two of the blocks 10, taken vertically, a form is set up and,'in the case of the pouring of the top section or portion of the wall, the concrete mixture is poured into the space between the form and the sheet pile structure from the top thereof.. This first section takes its initial set as the removal of the material proceeds. been removed, the form is lowered so as to rest upon the bottom of the excavation produced. the upper portion of this Vform overlapping the lower portion ofthe upper section of the wall which has been poured. rlhe concrete mixture is then forced into the space inclosed i. by the form, the first section of the wall, the

bottom of the excavation and the sheet pile struct-ure, in any suitable manner, the spacing blocks 10 being first properly placed before the form is erected. After this space has been completely filled with the concrete mixture under pressure, theremoval of the material proceeds, the form being again lowered and a third portion or sectionof the wall poured under pressure, the pouring of the walls thus proceeding asthe iemoval of the material proceeds. The advantage of this method is that the forms are comparatively small and can be quickly and easily handled, andall necessity for providing an elaborate system for bracing the forms is eliminated effecting a material saving in time and labor, as well as cost of material. ln Fig. 3 we have illustrated a wall 18 constructed in this manner an d formed in three sections 18h, 18C and 18d, v' respectively. For purposes of illustration these sections of the wall have been indicated as separate from each other. though, in practice, the sections will be poured successively and will be effectually united so 'as to forma monolithic structure.

rl`lie walls 18 form the foundation or lower portion of the permanent structure to be erected. ln constructing these walls the forms will be spaced from the pile structure the proper dista-nce to produce walls of the desired thickness to support the load of the superstructure. ln this connection, the vertical braces or I-beams 8 are of proper `strength to carry whichever is the greater load.; the earth thrust during construction or the load imposed by the completed struct-ure. Where circumstances require, other reinforcing members in addition to the I-beams 8, may be embedded in the walls 18 during pouring After the second vstep or batch hasA thereof. In this manner itispossible, by our method, to construct the supporting walls of the permanentA structure as removal of the material progresses, these walls being completed practically Vsimultaneously with the completion of removal of such material. This do this when the wall is poured in sections progressing downwardly with the progress of the reinovalof the material as the partially Y set wall section and the material thereof'between the piles and t-he'brace members is amply able toresist the inwardpressure to which. the pile structure is subjected, the upper portions of the brace members 8 being held against inward movement` by cross beamsl l24 associated with wales 11EL and wedges 16 driven between theplates 14 and 155, lThe wales l1CL` are formed of wooden beams but theyv may be replaced by the l-beams 11 of Figure 2, if desired.

Vliilerwe have illustrated and described wooden blocks as spacers between the p iles and the I-beains, any other suitable yor equivalentv means maybe employed for this purpose. Under certain conditions, as explained above and as illustrated in Fig. 3, the spacing meinbers between the piles and the braces `or I-beams may be omitted. It v`is also to be understood that Vany suitable-means other than the plates 9 may be employed to increase the bearing Acapacityiof the lower ends of the I- beams 8, such as, by way of example, by'driving short pieces of steel sheet pilin', steel plates, or other structural members immediately infront ofthe I-beams. These steel members could be burned off after completion ofthe excavation, if desirable.

iesV

The Colfer-dam thus constructed may be used as a foundation for a suitable superstructure as above set forth, or, if `it is to be used in connection with the construction of a platform, such asa wharf or other landing,

,through openings in wales 11b yand receive nuts 21 and washers 22 which hold the rodsV against outward movement.` 'Ihe outer end of each rod lpasses through an anchor member or deadman 23 buried in the soil, and receives a nut 24 and washer 25 which prevent Withdrawal of the rodfrom member 23. The rod includes a turnbuckle 26 by means of which proper tension can be placed on the rod Vto effectively brace the Lbeams 8 against inward movement. This form has the advantage of leaving the interior of the cofferdam entirely unobstructed, greatly facilitating excavation of the material and work within the dam.

In t-he form illustrated in Figure 8 the wales and all bracing have been omitted. This form is used in localities of good firm soil, and where the dam is relatively shallow. Under such conditions thecoifer-dam acts as a cantilever and is well able to withstand the strains to which'it is subjected by eXternal pressure, and all wales, cross braces, an

chor rods or other bracing of a similar nature are omitted.

In Figure 9 we have illustrated another modification inV which ythe cross braces or beams 27 are formedof concrete and are integrally united with the side walls 18 to form therewith a monolithic structure. One way of doing this is to first eXcavate the soil about the entire sheet piling structure to a depth corresponding to the ldepth'of the first section of the walls 18 to be' poured,-the`width of the trench thus formed corresponding to the thickness of the wall 18.V Intersecting trenches are then dug in the soil within the sheet piling structure, these trenches being at right angles to the walls of this structure and of a depth corresponding to the desired vertical thickness of the beams 27. These trenches open into the trench about the inner face of the sheet piling structure. All of the trenches are then filled with concrete which sets as the excavation of the material between the trenches proceeds. After the material has been excavated to the depth of the first section of the walls 18, suitable forms are set up and the succeeding section of the wall is poured, the pouring of the walls proceeding f progressively with the excavation of the soil,

as previously described. A` second method of constructing this form of dam is to remove the soil for the full cross-area of the enclosed space to a proper depth, after which suitable forms are set up and the cross-braces or beams 27 and the top section of the wallsy 18 are formed simultaneously. In either case, the walls and the cross-beams are integrally united and form a monolithic structure. Where necessary, or desired, the beams 27 can be provided with suitablereinforcing members, such as steel bars, embedded therein in a known manner. Preferably, though not necessarily, each of the beams 27 is formed with a rabbet 28 at each side and in its upper face. These rabbets are for reception of c0nother flat top structures. In cases where the beams 27 are of appreciable length or have to support heavy loads, suitably spaced columns 30 may be provided beneath these beams at the points of intersection thereof, and at other points also, if desired. In this construction we avoid the necessity of using wales or cross-braces whichare later removed, the beams 27 forming part ofthe permanent structure, this effecting a material saving in time, material, and work with a resulting saving in the total cost of the structure.

That we claim is i 1. In a coffer-dam, an l outer sheet pile structure, inner brace members'driven adjacent the pile structure, spacing means conlined betweenthe brace members and the pile structure, and an inner reinforcing wall enclosing and connecting the brace members,

said wall including as elements thereof said spacing lmeans confined between the brace' members and the pile structure.

2. The method of constructing a coffee dam and erecting a permanent structure thereon, consisting in driving a structure of sheet piles enclosing the material to beremoved, driving a plurality of brace members within and adjacent the sheet pile structure, inserting spacing means between the sheet pile structure and certain of the brace members, removing the enclosed material, and erecting walls between and about the brace members, the outer faces of the walls being defined bythe sheet pile structure, the brace members becomingA permanently associated with said walls and forming reinforcing ele ments therefor and the walls thus erected forming the foundation walls of the permanent structure.

In witness whereof we have hereunder subscribed our names this 24th day of October,

i WILLIAM S. MONROE. JOHN C. SANDERSON. 

